You can call Squamish forest office, but there's a massive slide on that road in the area of Buck that doesn't melt out until July. Seriously. If you went up there in May, the slide is about 200m across and 20 ft deep. This point is too far away from the start of the A-E traverse to make it worthwhile. I haven't heard of anyone doing this trip in the last few years since the slide started gushing. Too bad, I'd love to. Some folks on bivouac.com have pointed out the possibility of starting the traverse from the Elaho side of things, but this would be a bit exploratory I think. You could always start at Buck, go to Porterhouse and then come back. Best of luck